A. Field of the Invention
The present invention relates to the beneficiation of langbeinite and kieserite contained in certain ores, such as langbeinite ore from the Carlsbad Basin in New Mexico containing kieserite in various quantities from about 2 to 35%. Langbeinite and kieserite are both used as fertilizer ingredients. Langbeinite (K.sub.2 SO.sub.4.2MgSO.sub.4) is desirable for this purpose because it provides a source of potassium, magnesium and sulfur. Kieserite (MgSO.sub.4.H.sub.2 O) provides slowly water soluble magnesia which is useful for various purposes particularly as a fertilizer component. Langbeinite is customarily sold with a minimum guaranteed analysis of 22% K.sub.2 O (97% langbeinite) and kieserite is currently marketed with a minimum guaranteed analysis of 26% MgO.
B. Prior Art
A number of processes have been developed for the concentration or beneficiation of kieserite. U.S. Pat. No. 3,480,139 discloses a method for the flotation of kieserite after an electrostatic separation, using fatty acid amines as flotation agents. A number of German patents have been directed to the separation of kieserite from various contaminants. DAS No. 871,133 (1953) discloses a process for the flotation of kieserite containing potassium salts, using aliphatic amine and a magnesium sulfate carrier liquor. DAS No. 1,064,891 (1959) relates to the separation of kieserite from anhydrite (anhydrous calcium sulfate) using an unsaturated brine carrier liquor at a pH not above 6.8.
German Pat. DAS No. 1,144,213 (1963) teaches the use of amines and oleic acid in a 6:1 ratio for the flotation of kieserite in a water medium for the separation of kieserite from sylvinite ores.
German Pat. DAS No. 1,159,871 (1963) teaches the flotation of various mixtures of kieserite, langbeinite and anhydrite and says that the separation of kieserite from langbeinite is possible with pH values around the neutral point PH 7.0. The process requires low electrolyte liquors or water as the carrier liquor and fatty acid amines were used as the flotation agent. The process produced langbeinite of only 87% concentration.